Thermoelectric coolers are very sensitive to thermal loads of convection, conduction, and radiation types. For protection against convection and conduction type thermal loads, thermoelectric coolers have been inclosed in vacuum type packages (DEWARS, for example), but as the temperature of the thermoelectric cooler is substantially below that of the interior side of the vacuum package, the thermoelectric cooler remains subject to radiation type thermal loads.
To reduce the radiation type thermal load, upper stages of thermoelectric coolers have been enclosed in close fitting enclosures forming thermal radiation shields, which are mounted on the supporting substrates of the thermoelectric cooler. An aperture is provided in the top side of the housing through which, for example, thermal energy from a source thereof passes for detection by a detector mounted on the thermoelectric cooler for cooling to its operating temperature.
Thermoelectric coolers constructed as described above, typically achieve cold side temperatures as low as minus 100 degrees Celsius. They produce about 10 to 20 milliwatts of cooling power while consuming about 3 to 10 watts of power.
These known thermoelectric coolers have certain disadvantages. Namely, they are expensive to manufacture for applications requiring the use of the radiation shield. In addition to the cost of the radiation shield, the labor cost of assembly is increased because of the cost of mounting the shield on the substrate. Another disadvantage is the relative low operating efficiency of the known thermoelectric coolers.